This research project proposes to purify and characterize DNA polymerases from eukaryotic cells and study their roles in DNA replication. The DNA polymerases include calf thymus DNA polymerase-alpha and DNA polymerase-beta, yeast DNA polymerase I and yeast DNA polymerase II. Yeast is currently used as a model system for studying the roles of DNA polymerases in DNA replication in eukaryotes. The general approach used is to isolate and characterize DNA enzymes from yeast and study the interaction of each DNA enzyme with DNA polymerases in the replication of single-stranded circular bacteriophage DNA as well as yeast plasmid DNA. In addition to the DNA polymerases, the DNA enzymes studied in this laboratory are RNA polymerases, DNA dependent ATPases, RNAase H activities and DNA swivelase.